In general, HMD device outputs a content (e.g., video, media files, VR content, etc.) which has a 360 degree view. The user may view this content by moving their head in accordance with a locomotion of the content rendered thereof.
Consider a scenario: when a user is viewing the VR content, rendered by the HMD device, while travelling in a vehicle/when the vehicle is in motion, the various movements of the vehicle and the user may affect the field-of-view of the VR content, currently viewed by the user. In an example, if the user is viewing the portion of the VR content at an angle of 45 degrees and the vehicle makes a turn towards the right side due to which the position of the user (i.e., head movement, body position, etc.) relative to the vehicle also moves in the right side. This movement of the user and/or the vehicle causes the HMD device(s) to present the content (i.e., currently displayed) towards the right side which might not be intended by the user, therefore leading to an inadequate user experience.
Consider another scenario: when a user is viewing the VR content, rendered by the HMD device, when the vehicle is in not in motion, the various movements of the user may affect the field-of-view of the VR content, currently viewed by the user. In an example, if the user is viewing the VR content at some specific angle and then makes some movement like switching seats in the vehicle, the field-of-view of the VR changes due to the relative movement of the user.